This invention relates generally to a fuel vapor management system for a motor vehicle that is powered by an internal combustion engine and more particularly to a valve for isolating headspace of a fuel tank from a vapor storage canister.
A known on-board fuel vapor management system for an automotive vehicle comprises a vapor storage canister that collects volatile fuel vapors generated in headspace of a fuel tank by the volatilization of liquid fuel in the tank and a purge valve for periodically purging collected vapors from the canister to an intake system of the engine. A known type of purge valve, sometimes called a canister purge solenoid (or CPS) valve, comprises a solenoid actuator that is under the control of a microprocessor-based engine management system.
During conditions conducive to purging, the canister is purged of collected fuel vapors by communicating the canister to the engine intake system through the CPS valve. The CPS valve is opened by a signal from an engine management computer in an amount that allows intake manifold vacuum to draw volatile fuel vapors from the canister for entrainment with the combustible mixture passing into the engine""s combustion chamber space at a rate consistent with engine operation to provide both acceptable vehicle driveability and an acceptable level of exhaust emissions.
It is desirable to vent the canister to atmosphere to allow stored vapors to be more efficiently purged to the engine. It is known to communicate a vent port of a canister through a vent valve to atmosphere. The vent valve may be opened during certain conditions, such as during purging of the canister, and closed during other conditions, such as during a leak detection test.
In certain vapor management systems, the fuel tank headspace is in continuous communication with the canister. Other systems may call for the canister to be isolated from the tank headspace during certain conditions, in which case, the system may further comprise a tank isolation valve that, when open, allows free communication between the tank headspace so that vapors can pass from the tank to the canister, and that, when closed, disallows free communication to isolate the tank headspace from the canister.
It is known to mount such an isolation valve in a generally vertical orientation and at a location in a vehicle that is remote from the fuel tank.
It is believed that a tank isolation valve that can be mounted directly on a fuel tank and in a generally vertical orientation can provide certain benefits in the design of an automotive vehicle fuel system and associated vapor management system, especially if the valve is more vertically compact, and/or is capable of being partially disposed within the interior of a fuel tank. An isolation valve that is more vertically compact and/or capable of being partially disposed within a depression in a tank wall can present a lower external profile when the tank and valve are viewed in vertical elevation. It is believed that such a lower profile can be useful to vehicle designers in packaging various components of the vehicle in and adjacent the fuel tank.
Principles of the invention, as disclosed herein, provide a low-profile tank isolation valve possessing these attributes and capabilities.
In one general respect, the present invention relates to a fuel vapor management system for an internal combustion engine fuel system wherein fuel vapor generated by the volatization of fuel in a fuel tank is collected in a vapor storage canister that is purged to the engine during conditions conducive to purging. Headspace of the fuel tank is selectively communicated to the vapor storage canister through a tank isolation valve. When open, the valve allows free communication between the tank headspace and the canister so that volatile vapor can pass from the tank to the canister, and when closed, the valve disallows free communication to thereby isolate the tank headspace from the canister.
The valve comprises a body mounted on a wall of the tank in enclosing relation to an opening in the tank wall. The valve has an inlet port communicated to the tank headspace at the tank wall opening, an outlet port, and a flow passage through which vapor entering the inlet port from the headspace can be conveyed to the outlet port. A valve seat circumscribes the flow passage, and a closure selectively seats on, and unseats from, the valve seat to selectively close, and open, the flow passage. An operating mechanism comprises an electric actuator that is selectively energized by electric current and an armature that is selectively positioned by the selective energization of the actuator to selectively operate the closure to seat on, and unseat from, the valve seat. An element that is disposed between the armature and the closure operatively relates the armature to the closure. The armature comprises a cylindrical walled tube that is open at opposite axial ends and is selectively positioned within the body along a straight axis coincident with the tube axis. The element constrains vapor flowing through the flow passage to pass through the armature tube when the closure is unseated from the seat.
In another respect, the present invention relates to a valve, as just described, for venting tank headspace.
In another general respect, the present invention relates to a fuel vapor management system as defined above wherein the tank isolation valve comprises an inlet port communicated to the tank headspace at the tank wall opening, an outlet port, and a flow passage through which vapor entering the inlet port from the headspace can be conveyed to the outlet port. A valve seat circumscribes the flow passage, and a closure selectively seats on, and unseats from, the valve seat to selectively close, and open, the flow passage. An operating mechanism comprises an electromagnet coil that is selectively energized by electric current to selectively position an armature coaxially with respect to a central through-hole of the coil to cause the closure to seat on, and unseat from, the valve seat. The seat and the closure are disposed within the coil through-hole, and the armature comprises a through-passage having opposite ends, one of which is disposed within the through-hole and is toward the closure and the other of which is toward one of the ports, to provide for vapor that passes from the inlet port to the outlet port when the closure is unseated from seat to pass through the through-passage in the armature.
In another respect, the present invention relates to a valve, as described in the immediately preceding paragraph, for venting tank headspace.
Additional aspects of the invention relate to various constructional details of the valve.
The foregoing, along with additional features, advantages, and benefits of the invention, will be seen in the ensuing description and claims which should be considered in conjunction with the accompanying drawings. The drawings disclose a presently preferred embodiment of the invention according to the best mode contemplated at this time for carrying out the invention.